Autoimmune disorders are a significant and widespread medical problem. For example, rheumatoid arthritis (RA) is an autoimmune disease affecting more than two million people in the United States. RA causes chronic inflammation of the joints and typically is a progressive illness that has the potential to cause joint destruction and functional disability. The cause of rheumatoid arthritis is unknown, although genetic predisposition, infectious agents and environmental factors have all been implicated in the etiology of the disease. In active RA, symptoms can include fatigue, lack of appetite, low grade fever, muscle and joint aches and stiffness. Also during disease flare ups, joints frequently become red, swollen, painful and tender, due to inflammation of the synovium. Furthermore, since RA is a systemic disease, inflammation can affect organs and areas of the body other than the joints, including glands of the eyes and mouth, the lung lining, the pericardium, and blood vessels.
Traditional treatments for the management of RA and other autoimmune disorders include fast acting “first line drugs” and slower acting “second line drugs.” The first line drugs reduce pain and inflammation. Example of such first line drugs include aspirin, naproxen, ibuprofen etodolac and other nonsteroidal anti-inflammatory drugs (NSAIDs), as well as corticosteroids, given orally or injected directly into tissues and joints. The second line drugs promote disease remission and prevent progressive joint destruction and are also referred to as disease-modifying anti-rheumatic drugs or DMARDs. Examples of second line drugs include gold, hydrochloroquine, azulfidine and immunosuppressive agents, such as methotrexate, azathioprine, cyclophosphamide, chlorambucil and cyclosporine. Many of these drugs, however, can have detrimental side-effects. Thus, additional therapies for rheumatoid arthritis and other autoimmune disorders have been sought.
More recently, biological therapies have been applied to the treatment of autoimmune disorders such as rheumatoid arthritis. For example, three TNFα inhibitors, REMICADE™ (infliximab), a chimeric anti-TNFα mAb, ENBREL™ (etanercept), a TNFR-Ig Fc fusion protein, and HUMIRA™ (adalimumab), a human anti-TNFα mAb, have been approved by the FDA for treatment of rheumatoid arthritis. While such biologic therapies have demonstrated success in the treatment of rheumatoid arthritis and other autoimmune disorders, not all subjects treated respond, or respond well, to a TNFα inhibitor. The use of TNFα inhibitors such as TNFα inhibitors typically is more expensive than traditional treatments and usually requires administration by injection, which, at least for certain agents, may require that the patient visit a medical office on a frequent basis. Thus, it would be very helpful to predict in advance of treatment whether a rheumatoid arthritis patient is likely to be responsive to treatment with a TNFα inhibitor. Accordingly, ways for predicting responsiveness to a TNFα inhibitor in patients having autoimmune disorders, such as rheumatoid arthritis patients, are of particular interest.